Frequency modulations are an important acoustic component of the communication vocalizations of many species, including humans and bats. For bats, they are also an important component of the echolocation calls, and most of the neurophysiological research regarding FM processing in bat auditory system has been conducted with the aim of understanding how FM processing contributes to echolocation. How FM processing contributes to the recognition of communication sounds is poorly understood, despite their more general relevance to mammalian hearing. In this study, neural responses of single cells in the bats auditory system will be examined with FM stimuli. The selectivity of cells to parameters of FM sound such as direction (up or down) and slope will examined. Neural mechanisms for the creation of such selectivity will also be explored. The location of the cells to be studied will be the monaural nuclei of the lateral lemniscus, a group of nuclei about which relatively little is known. These nuclei are believed to be involved in precise temporal coding of sounds, so they could very well be important for the coding of patterns of complex sounds such as communication vocalizations.